4th-Unit 2 Lesson 2 Section 1

Learning Objective

​4-PS3-3 I can ask questions and predict outcomes about the changes in energy (ex. speed) that occur when objects collide.

​Vocabulary for the lesson

​Collide-To touch something while moving. A moving object hitting another object is called a collision.

Open Ended

What does the word collide mean? give me two examples.

Open Ended

​Two soccer balls of the same size and weight.

One ball collides with the non-moving ball. List two scientific questions that you can ask about this scenario.

Open Ended

​Two soccer balls of the same size and weight.

One ball collides with the non-moving ball. What is your prediction for this scenario.

​Let's test it!

​Energy Is Transferred and Conserved

​After soccer practice, you collect soccer balls from the field. You roll one ball straight at another ball that is still. The rolling ball hits the still one, and a curious thing happens. The two balls seem to trade motions. The rolling ball stops moving at the exact spot where the two balls meet. The ball that was still rolls in the direction that the other ball had been rolling. What caused this to happen?

Open Ended

What caused this to happen?

​The energy of the moving ball transfers to the still ball when they collide. With the energy it gains during the collision, the ball that was still now is set in motion. The ball that was moving now is still.

​The two balls moved the way they did because they collided. To collide is to touch something while moving. Energy transfers from one object to another when objects collide. Recall that all moving objects have energy of motion. So, the first ball, which is rolling, has energy of motion, but the second ball, which is still, has none. At the moment when the balls collide, the forces between them cause the first ball to slow down and the second ball to move. When this happens, the first ball's energy shifts to the other ball. The second ball now has energy, while the first no longer has energy of motion. So, its motion has stopped.

Multiple Choice

Collide means to touch something while moving. A moving object hitting another object is called a collision.

• True

• False

​Because of the collision, the speeds of both balls changed, and so did their energy. However, the total amount of energy did not change because energy is always conserved, even during a collision.

Poll

According to our text Is energy created or destroyed?

• Its created but not destroyed

• its not created but it can be destroyed

• it can not be created or destroyed. It can only be transferred

Open Ended

What happens to the energy of a ball that is rolling and hits a ball that isn't moving? Explain in detail.

​Complete the questions in TCI Unit 2 Lesson 2 Section 1